Frangible barrier

ABSTRACT

A frangible boom assembly for vehicular tollway barriers is mounted to a boom actuating apparatus for pivotal movement between a barrier position transverse to a direction of traffic flow and a generally upright position to allow an authorised vehicle to pass. The frangible boom assembly is pivotally mounted to the actuation apparatus whereby in use, contact between a vehicle and the boom, when in a barrier position, causes said boom to swing away from the vehicle in the direction of traffic flow to reduce the possibility of damage to the boom member and/or the vehicle.

BACKGROUND OF THE INVENTION

[0001] THIS INVENTION is concerned with frangible barriers for motor vehicle traffic control.

[0002] The invention is particularly, although not exclusively, concerned with frangible barriers for toll booths on tolled motorways.

[0003] Passage through a traffic lane of a toll collection station is usually controlled by a boom moveable between a horizontal barrier position and an upright ‘free to pass’ position.

[0004] The boom is activated by the collection and validation of the correct toll coinage whereby a coin receiver and validation apparatus sends a signal to the boom actuation apparatus to elevate the boom. The presence, or absence, of a vehicle adjacent the boom, and the passage of an authorized vehicle, is determined by optical and/or proximity sensors to close the boom after an authorized vehicle has passed through.

[0005] While generally effective for their intended purpose, prior art traffic control booms suffer a number of disadvantages.

[0006] Many impatient drivers tend to anticipate the upward movement of a boom within a short period of time after placing the toll coinage in a collection hopper. Either misanticipation or misjudgement of the proximity of a boom leads to contact between the vehicle and the boom resulting in scratched paint on the vehicle, damaged radio aerials and/or damaged windscreens and, frequently, broken booms.

[0007] Apart from the cost and inconvenience of frequent boom replacement, tollway operators incur very substantial insurance premiums for vehicle damage caused by lane control booms. In addition, tollway operators can face loss of revenue if a lane has to be closed for repairs during a busy period.

[0008] The most commonly employed boom comprises a breakable timber beam about 15 mm in thickness and tapering from a width of about 75 mm at a free end to about 150 mm at a supported pivot end. A low inertial mass is required to permit rapid movement of the arm from a horizontal rest position to a vertical position and back again without undue loads or stresses on the actuating mechanism.

[0009] In order to reduce the costs associated with prior art breakable timber booms, a frangible tubular aluminium boom mounted on a vertical pivot axis has been proposed.

[0010] The frangible boom has a tubular bushing aligned with apertures in the tubular member on an upright axis. The boom is mounted for pivotal movement on an upright axis through about 90° by means of a bolt extending through aligned apertures in the boom and a mounting bracket on the elevating mechanism.

[0011] When contacted by a vehicle, the boom pivots about the upright axis in the direction of travel of the vehicle thus avoiding breakage. A microswitch coupled between the boom and the bracket deactivates the boom elevation mechanism when the boom is swung away from its normal rest position extending transversely of a traffic lane.

[0012] While generally satisfactory for its intended purpose, these prior art aluminium booms are prone to breakage in the region of the aligned apertures through which the upright mounting pivot bolt extends. It is believed that failure of the boom occurs as a result of stresses localized around the pivot bolt apertures, the stresses arising from inertial forces imposed by the rapid acceleration and deceleration of the boom actuating mechanism.

SUMMARY OF THE INVENTION

[0013] It is an aim of the present invention to overcome or ameliorate at least some of the problems faced with prior art frangible boom assemblies.

[0014] According to one aspect of the invention there is provided a frangible boom assembly comprising:

[0015] a tubular boom member receivably located in a tubular socket, said tubular socket being supported in a mounting for pivotal movement about an upright axis; and

[0016] a boom mounting associated with said tubular socket, said boom mounting extending orthogonally to said upright axis.

[0017] Suitably, the tubular boom member is comprised of an aluminium or aluminium alloy metal.

[0018] The tubular boom may be of any desired cross-sectional shape.

[0019] Preferably, the tubular boom has a generally circular cross-section.

[0020] The tubular boom is suitably a neat sliding fit into said tubular socket.

[0021] The tubular boom may be releasably located in said tubular socket.

[0022] The boom mounting may comprise a bracket member attachable, in use, to a boom actuator.

[0023] Suitably, the tubular socket is supported in said boom mounting for pivotal movement by socket and spigot members aligned on an upright axis.

[0024] The boom mounting suitably includes removable fasteners extending transversely of said boom orthogonal to said upright axis.

[0025] Preferably said tubular boom, in use, is pivotal from a barrier position, transverse to a direction of flow of traffic, to a free position substantially parallel to the direction of flow of traffic.

[0026] Suitably said boom is retainable in said barrier position by releasable engagement means.

[0027] Preferably, said boom includes cushioned impact absorption means extending over at least portion of its unsupported length.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order that the invention may be more clearly understood and put into practical effect, reference will now be made to a preferred embodiment illustrated in the accompanying drawings in which:

[0029]FIG. 1 shows a partial top plan view of a boom support arrangement in a secured position;

[0030]FIG. 2 shows the boom support arrangement of FIG. 1 in a free position;

[0031]FIG. 3 shows a side elevational view of the arrangement of FIGS. 1 and 2;

[0032]FIG. 4 shows a cross-sectional view through A-A in FIG. 1; and

[0033]FIG. 5 shows a cross-sectional view through B-B in FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

[0034] In FIG. 1, the boom support assembly 1 comprises an adaptor bracket 2 secured to boom support arm 3 attached to rotatable actuator arm 4 of a conventional boom actuating mechanism 5.

[0035] A tubular steel socket 6 slidably receives a tubular aluminium alloy boom 7 (shown in phantom) with an inner free end of boom 7 being frictionally engaged in a clamp 8. Threaded steel nuts 9 are welded or brazed to socket 6 and threadably receive bolts (not shown) which extend through aligned transverse apertures in boom 7 to secure the boom into socket 6.

[0036] Socket 6 is pivotally mounted in adaptor bracket 2 for pivotal movement about an upright axis by means of threaded nuts 10 secured to opposing inner faces of channel-like adaptor 2. Set screws (not shown) extend via apertures 11 in bracket 2 into nuts 10 to engage against the outer surface of socket 6 to effect locking of the set screws (not shown).

[0037]FIG. 2 is a plan view of the arrangement of FIG. 1 in a free position with the inner end 7 a of boom 7 in a disengaged position.

[0038]FIG. 3 is a side elevational view of the arrangement of FIGS. 1 and 2.

[0039] In FIG. 3, the free end 7 a of boom 7 is frictionally engaged in a resilient polymeric clamp 8, suitably of polyurethane or the like, secured in adaptor 2 by screws 12.

[0040] Pivotal mounting of socket 6 is effected by set screws 13 extending via opposed apertures 11 in adaptor 2 for engagement in nuts 10. Set screws 13 are locked by frictional engagement of a free end with the outer surface of socket 6, and thereby resist disengagement as the boom pivots.

[0041]FIGS. 4 and 5 respectively, show cross-sectional views through A-A and B-B in FIG. 1.

[0042] In the event that a vehicle contacts the outer end portion of boom 7, the impact will cause the boom 7 and associated socket 6 to pivot about an upright axis in which set screws 13 lie.

[0043] As there is no penetration of the boom 7 by set screws 13, the upper and lower surfaces of boom 7 maintain their structural integrity. Accordingly, with constant working of the boom in a vertical plane, the stresses in the upper and lower surfaces of the boom tube are evenly and fully dispersed without the tendency for stress cracking around upper and lower mounting apertures as otherwise occurs in prior art booms.

[0044] Although not shown for the sake of simplicity, the frangible boom arrangement according to the invention is fitted with a proximity sensor to maintain the boom actuator circuit in an active state. In the event of impact, the boom swings into a direction parallel to traffic flow and deactivates the boom actuator. Once the boom is returned to the secured position by an attendant, the actuator is reactivated by the proximity switch.

[0045] Also not shown is a protective cushioning about the free outer end of the boom. Suitably, a layer of polymeric energy absorbing foam is wrapped around the boom and a protective plastics sheath bearing reflective indicia is secured about the foam layer. In combination, the foam layer and the plastics sheath substantially reduce impact and abrasion damage to vehicles which encounter the boom.

[0046] It readily will be apparent to a skilled addressee that many modifications and variations may be made to the invention without departing from the spirit and scope thereof.

[0047] Throughout this specification, unless the context requires otherwise, the word ‘comprise’ and variations such as ‘comprises’ or ‘comprising’, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers. 

1. A frangible boom assembly comprising: a tubular boom member receivably located in a tubular socket, said tubular socket being supported in a mounting for pivotal movement about an upright axis; and a boom mounting associated with said tubular socket, said boom mounting extending orthogonally to said upright axis.
 2. An assembly as claimed in claim 1 wherein the tubular boom member is comprised of an aluminium or aluminium alloy metal.
 3. An assembly as claimed in claim 1 wherein the tubular boom is of a generally polygonal cross-sectional shape.
 4. An assembly as claimed in claim 1 wherein the tubular boom has a generally circular cross-section.
 5. An assembly as claimed in claim 1 wherein the tubular boom is a neat sliding fit into said tubular socket.
 6. An assembly as claimed in claim 1 wherein the tubular boom is releasably located in said tubular socket.
 7. An assembly as claimed in claim 1 wherein the mounting comprises a bracket member attachable, in use, to a boom actuator.
 8. An assembly as claimed in claim 1 wherein the tubular socket is supported in said boom mounting for pivotal movement by socket and spigot members aligned on said upright axis.
 9. An assembly as claimed in claim 1 wherein the boom mounting means suitably includes removable fasteners extending transversely of said boom orthogonal to said upright axis.
 10. An assembly as claimed in claim 1 wherein said tubular boom, in use, is pivotal from a barrier position, transverse to a direction of flow of traffic, to a free position substantially parallel to the direction of flow of traffic.
 11. An assembly as claimed in claim 10 wherein said boom is retainable in said barrier position by releasable engagement means.
 12. An assembly as claimed in claim 1 wherein said boom includes cushioned impact absorption means extending over at least portion of its unsupported length.
 13. A method of mounting a boom member to a boom actuation apparatus, said boom actuation apparatus being operable to selectively move said boom member between a barrier position transverse to a direction of traffic flow and a generally upright position to allow an authorised vehicle to pass, said method characterised in that the boom member is pivotally mounted to said actuation apparatus about an upright pivotal axis when said boom member is in a barrier position whereby in use contact between said boom member in a barrier position and a vehicle moving past said boom actuating apparatus causes said boom member to swing away from said vehicle in the direction of flow of traffic. 